powerpc: Fix pciconfig_iobase system call on PCI-Express powermac

X has been failing to start on my quad G5 powermac since commit
1fd0f52583a85b21a394201b007bc1ee104b235d ("powerpc: Fix domain numbers
in /proc on 64-bit") went in.  The reason is that the change allows X
to see the PCI-PCI bridge above the video card (previously it was
obscured by the fact that there were two "00" directories in
/proc/bus/pci), and the pciconfig_iobase system call on the bridge is
failing because of a hack that we have to return information about the
AGP bus when X asks about bus 0.  This machine doesn't have an AGP bus
(it has PCI Express) and so the pciconfig_iobase call is returning -1,
which ultimately causes X to fail to start.

This fixes it by checking that we have an AGP bridge before
redirecting the pciconfig_iobase call to return information about the
AGP bus.  With this, X starts successfully both on a quad G5 with
PCI Express and on an older dual G5 with AGP.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
index 39fadc6e1492..586962f65c2a 100644
--- a/arch/powerpc/kernel/pci_64.c
+++ b/arch/powerpc/kernel/pci_64.c
@@ -560,9 +560,14 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
          * G5 machines... So when something asks for bus 0 io base
          * (bus 0 is HT root), we return the AGP one instead.
          */
-        if (machine_is_compatible("MacRISC4"))
-                if (in_bus == 0)
+        if (in_bus == 0 && machine_is_compatible("MacRISC4")) {
+                struct device_node *agp;
+
+                agp = of_find_compatible_node(NULL, NULL, "u3-agp");
+                if (agp)
                         in_bus = 0xf0;
+                of_node_put(agp);
+        }
 
         /* That syscall isn't quite compatible with PCI domains, but it's
          * used on pre-domains setup. We return the first match